This invention relates to the field of variable area flow restrictors. More particularly, this invention relates to variable area flow restrictors which exhibit a linear relationship between flow and pressure drop across the restrictor.
In many applications it is desired to obtain a linear relationship between variations in flow and variations in pressure drop across a restrictor in a line. However, a typical fixed area flow restrictor in a line results in a flow-pressure drop relationship in which the flow varies as a function of the square of the pressure drop across the restrictor.
In order to obtain a linear relationship between flow and pressure drop across a restrictor, the prior art has resorted to devices known as laminar type restrictors. Laminar type restrictors are pipes or conduits stuffed with fibrous material, and these devices exhibit a linear relationship between changes in flow and changes in pressure drop across them. However, these laminar devices of the prior art encounter a serious problem in that they get "wet". That is, they get soaked with the fluid flowing in the line or the vapor of the fluid flowing in the line, or they get dirty because they act somewhat like a filter. Therefore, over a period of time, these laminar type devices of the prior art exhibit serious and unacceptable shifts in performance and response.
Accordingly, there is a definite need for a simple and reliable restrictor which will exhibit a linear relationship between flow and pressure drop for various applications.